Republican Pat Toomey is leading Democrat Joe Sestak 45 percent to 36 percent, according to a recent Public Polling Policy survey. In June, the same poll showed the candidates in a dead heat, both with 41 percent.

The pollsters credit Toomey's lead to three factors:

-He has a 50-23 lead with independent voters.

-He's benefiting from a much more unified party, as he leads 74-9 with Republicans while Sestak is currently up only 64-15 with Democrats.

-This is our first poll of the race explicitly surveying likely voters and given the considerably greater enthusiasm on the Republican side we're seeing an electorate in the state that voted for John McCain by a point in 2008, in contrast to Barack Obama's actual 10 point victory in the state.